Estimate and return either the traffic speed or the car entries in the city of Thessaloniki using historical traffic data. It's used in transport pilot <http://trafficstatusprediction.imet.gr/> of the 'BigDataEurope' project <https://www.big-data-europe.eu/>. There are functions for processing these data, training a neural network, select the most appropriate model and predict the traffic speed or the car entries for a selected time date.